The present invention relates to sensors and, more particularly, to sensors for position detection systems.
Vehicle occupant position detection systems are useful in connection with air bags and other pyrotechnically deployed restraints as a means of determining when, and with what force, a restraint should be deployed. In general, such systems include an emitter for emitting one of more beams of infrared energy (wavelengths between 700 nanometers and 1100 nanometers) to define a corresponding number of viewing fields and a receiver having a sensor for receiving the reflected energy to detect the presence of an occupant or target within the viewing fields. The sensor converts the focused light energy reflected from the target into position relative, electrical sensor currents. The sensor currents are used by the vehicle occupant position detection system to determine the distance of the target from the system.
The prior art sensor includes a single 10 millimeter by 10 millimeter active area for receiving the reflected light energy. Further, the prior art sensor requires an optical separation between the emitter and the receiver approximately equal to or greater than 70 millimeters. As a result, the system, including the emitter and receiver, has a relatively large package size. Attempts to decrease the package size by shortening the optical separation between the transmitter and the receiver result in reduced sensor resolution. Accordingly, it would be desirable to provide a sensor for a position detection system having greater resolution and a smaller package size.
The present invention provides a sensor including at least two active areas for receiving light energy and a resistive layer disposed on each of the at least two active areas for providing a pair of current signals corresponding to a position of light energy of a predetermined wavelength striking the active area.
The two or more active areas are electrically isolated from each other and operate independent of each other. Preferably, the two or more active areas are electrically isolated with silicon dioxide.